The present invention relates to boring tools for underground boring, and more particularly, it relates to pneumatic impact operated boring tools for use with horizontal boring machines during horizontal boring operations for placement of utility lines and the like.
Pneumatic impact-operated boring tools are well-known in the art. U.S. Pat. No. 3,756,328 issued to Sudnishnikov et al. discloses one such device. Typically, pneumatic impact-operated boring tools are used for burrowing holes in soil, particularly horizontal or near horizontal passages for installation of utility lines when trenching is undesirable. An example of such usage would be for the installation of services underneath an existing structure, such as a driveway or highway, where installation of the line by traditional open cut methods would be impractical. In this situation, the pneumatic impact-operated boring tool is launched from a pit on one side of the structure and is advanced to a receiving pit on the opposite side of the structures.
As the name implies, such boring tools function by impact. The tools possess a striking member (striker) slidable within a cylindrical housing. The striker delivers impacts on a surface at the front end of the housing. This impacting motion within the tool itself causes the soil around the tool to compact away from the nose of the housing, thus forming a hole. The tools are typically driven by a compressed air source. As the compressed air flows through the tool, the striker will be driven in a reciprocal motion generating a series of rapid impacts against the front of the tool housing, causing it to be driven through the ground.
Utility service lines to be installed may either be inserted into the hole formed by the piercing tool, or may be pulled into the hole behind the tool as it operates. Alternatively, pneumatic piercing tools have also been used to install rigid service lines such as steel lines by driving the steel line into place.
It is occasionally desirable to retract the piercing tools from the borehole being formed. For example, if the piercing tool encounters an obstruction in the soil such as a rock or stone or deviates from the desired path or is damaged in any way, quick withdrawal of the tool from the borehole may be necessary. Most tools are designed to facilitate this retraction by having a mode wherein the striker impacts the rear of the tool causing a retrograde progression of the tool within the borehole.
Thus, reversible impact-operated boring tools are also well-known in the art. U.S. Pat. No. 4,683,960 issued to Kostylev et al. discloses such a device. The prior art discloses various means for accomplishing the reverse motion. In the older designs, the shift from the forward operation mode of the tool to the reverse/withdraw mode is accomplished in any one of the following ways. Some require interrupting the pressurized fluid supply. Others require manipulation of the hose supplying the pressurized fluid to the tool, either by rotating the hose or by pulling it back. Still others require both the interruption of the pressurized fluid supply and the manipulation of the hose.
However, there are several disadvantages associated with these processes. For example, when the pressurized fluid supply is interrupted and the tool is therefore momentarily shut off, the tool may not restart when the pressurized fluid supply is recommenced. In tools requiring hose manipulation, when the hose is flexible, it is often difficult to relate the degree of rotational motion of the hose at the surface to the degree of rotational motion at the tool itself, which may be some distance away. In addition, cave-ins of the hole wall can bind the hose, making it difficult to rotate the hose, or preventing it altogether. Consequently, it is often difficult to reverse the operation of the tool, or to be certain of the direction of operation.
In the more recent designs, the mechanism of shifting the pneumatic tool from forward to reverse is somewhat simplified. U.S. Pat. No. 5,172,771 (""771 patent) and U.S. Pat. No. 5,327,636 (""636 patent), both issued to Wilson and both incorporated fully herein by reference, disclose such a device. In Wilson""s ""771 patent, a second air hose was added to act as a control mechanism for switching the tool from forward to reverse. Pressurizing the control hose caused a valve mechanism in the tool to move to a forward position, creating the forward movement of the pneumatic tool. Releasing the pressurized air from the control hose caused the valve mechanism to move to a rearward position, resulting in a reverse/withdrawal movement of the tool. However, the valving mechanism in the tool of the ""771 patent is complex, and difficult to assemble, requiring assembly of several parts such as a pre-load spring, snap ring, etc. for valve containment. Additionally, the valving mechanism of the ""771 patent is rigid in terms of deflection perpendicular to the longitudinal axis of the tool body. This inherent rigidity of the valving member makes the tool more prone to stalling if the tool body is deflected along its longitudinal axis by contact with an underground obstacle.
Due to the complexity presented by the current means for the reversing operation of impact-operated boring tools, and the increased labor and time associated with servicing the various component parts, an alternate simpler mechanism for switching a pneumatic piercing tool from forward to reverse operation is needed.
In one aspect, the invention relates to an impact-operated, ground-penetrating tool powered by a primary supply of pressurized fluid, and controlled between a forward operating mode and a reverse operating mode by a second supply of pressurized fluid. The tool comprises a housing, a striker, a manifold, a primary inlet tube, a valve chamber, and a control sleeve. The housing has a front end, a rear end, and body. The body of the housing defines an interior operating chamber with an inner surface, an exhaust conduit to provide fluid communication between the operating chamber and the outside of the tool, a forward striker surface, and a rearward striker surface.
The striker is reciprocally supported within the operating chamber of the housing between the forward and rearward striker surfaces. The striker has a forward end, a rear portion terminating in a rear end, and a striker body defining an interior striker chamber. The rearward portion of the striker sealingly engages the inner surface of the operating chamber to divide the operating chamber into a forward operating chamber and a rearward operating chamber. The rearward operating chamber is continuous with the exhaust conduit. Whereas, the striker body has at least one striker port to provide fluid communication between the forward operating chamber of the housing and the interior striker chamber.
The manifold is located near the rear end of the housing and comprises a primary conduit connectable to the primary fluid supply and a secondary conduit connectable to the secondary fluid supply. A primary fluid inlet tube extends from primary conduit of the manifold. Additionally, the valve chamber is in fluid communication with the secondary conduit in the manifold.
The control sleeve has a rear portion, a front portion, and an interior sleeve chamber defining a passage between the rear portion and the front portion. The front portion of the control sleeve is slidably and sealingly supported inside the rear portion of the striker. Whereas, the rear portion of the control sleeve is slidably and sealingly supported on the primary fluid inlet tube at least partially inside the valve chamber. The control sleeve provides continuous fluid communication between the primary fluid inlet tube and the striker chamber, so that in response to supply of primary fluid the striker reciprocates between a forward position and a rearward position. In the forward position, the striker port is open between the interior striker chamber and the forward operating chamber. Whereas, in the rearward position, the striker port is open between the forward operating chamber and the rearward operating chamber and the exhaust conduit.
Finally, the rear portion of the control sleeve includes a nodular lobe inside the valve chamber that is movable between a forward position in response to pressurization of the valve chamber and a reverse position in response to depressurization of the valve chamber. This causes the forward portion of the control sleeve to move between a forward position in which the striker hits the forward striker surface as it reciprocates and a rearward position in which the striker hits the rearward striker surface as it reciprocates.
In another aspect, the invention relates to an impact-operated, ground-penetrating tool powered by a primary supply of pressurized fluid, and controlled between a forward operating mode and a reverse operating mode by a second supply of pressurized fluid. The tool comprises a housing, a striker, a means for operably connecting the primary fluid supply, a valve chamber, a means for operably connecting the secondary fluid supply and a control sleeve. The housing has a front end, a rear end, and body. The body defines an interior operating chamber with an inner surface, an exhaust conduit providing communication between the operating chamber and the outside of the tool, a forward striker surface and a rearward striker surface.
A striker is reciprocally supported within the operating chamber of the housing between the forward and rearward striker surfaces. The striker has a forward end, a rear portion terminating in a rear end, and a striker body defining an interior striker chamber. The rearward portion of the striker sealingly engages the inner surface of the operating chamber to divide the operating chamber into a forward operating chamber and a rearward operating chamber. The rearward operating chamber is continuous with the exhaust conduit and the striker body has at least one striker port to provide fluid communication between the forward operating chamber and the interior striker chamber.
The means for operably connecting the primary fluid supply connects the primary fluid supply to the interior striker chamber. Additionally, the means for operably connecting the secondary fluid supply connects the secondary fluid supply to the valve chamber at the rear end of the housing.
The control sleeve has a rear portion and a front portion. The front portion of the control sleeve is slidably and sealingly supported inside the rear portion of the striker. Whereas, the rear portion of the control sleeve is slidably and sealingly received at least partially inside the valve chamber. The control sleeve provides continuous fluid communication between the means for operably connecting the primary fluid supply and the interior striker chamber. As a result, in response to supply of primary fluid the striker reciprocates between a forward position and a rearward position. In the forward position, the striker port is open between the interior striker chamber and the forward operating chamber. Whereas, in the rearward position, the striker port is open between the forward operating chamber and the rearward operating chamber and the exhaust conduit.
Finally, the rear portion of the control sleeve includes a nodular lobe inside the valve chamber that is movable between a forward position in response to pressurization of the valve chamber and a reverse position in response to depressurization of the valve chamber. This causes the forward portion of the control sleeve to move between a forward position in which the striker hits the forward striker surface as it reciprocates, and a rearward position in which the striker hits the rearward striker surface as it reciprocates.
In yet another aspect, the invention is an impact-operated, ground-penetrating tool powered by a primary supply of pressurized fluid, and controlled between forward operating mode and a reverse operating mode by a second supply of pressurized fluid. The tool comprises a housing, a striker, a primary connecting assembly, a valve chamber, a secondary connecting assembly and a control sleeve. The housing having a front end, a rear end, and body defining an interior operating chamber with an inner surface, an exhaust conduit providing communication between the operating chamber and the outside of the tool, a forward striker surface, and a rearward striker surface.
A striker is reciprocally supported within the operating chamber of the housing between the forward and rearward striker surfaces. The striker has a forward end, a rear portion terminating in a rear end, and a striker body defining an interior striker chamber. The rearward portion of the striker sealingly engages the inner surface of the operating chamber to divide the operating chamber into a forward operating chamber and a rearward operating chamber. The rearward operating chamber is continuous with the exhaust conduit and the striker body has at least one striker port to provide fluid communication between the forward operating chamber and the interior striker chamber.
The primary connecting assembly operably connects the primary fluid supply to the interior striker chamber. Whereas, the secondary connecting assembly operably connects the secondary fluid supply to the valve chamber located at the rear end of the housing.
The control sleeve has a rear portion and a front portion. The front portion of the control sleeve is slidably and sealingly supported inside the rear portion of the striker. Whereas, the rear portion is slidably and sealingly received at least partially inside the valve chamber. The sleeve provides continuous fluid communication between primary connecting assembly and the interior striker chamber. As a result, in response to supply of primary fluid the striker reciprocates between a forward position and a rearward position. In the forward position, the striker port is open between the interior striker chamber and the forward operating chamber. Whereas, in the rearward position, the striker port is open between the forward operating chamber and the rearward operating chamber and the exhaust conduit.
Finally, the rear portion of the control sleeve includes a nodular lobe inside the valve chamber that is movable between a forward position in response to pressurization of the valve chamber and a reverse position in response to depressurization of the valve chamber. This causes the forward portion of the control sleeve to move between a forward position in which the striker hits the forward striker surface as it reciprocates, and a rearward position in which the striker hits the rearward striker surface as it reciprocates.
In another aspect, the invention is a reversible impact ground penetrating boring tool comprising a housing, a striker, a primary fluid supply assembly, a control sleeve, and a secondary fluid supply assembly. The housing has a rear end, and an interior chamber defining a forward striker surface and a rearward striker surface.
The striker has an external wall surrounding an interior striker chamber. The striker is slidably and sealingly receivable within the interior chamber of the housing and is adapted to reciprocally move between the forward striker surface and the rearward striker surface. The external wall of the striker and the interior chamber of the housing define an operating chamber. The primary fluid supply assembly is operably connectable to the striker and is adapted to provide pressurized primary fluid to the interior striker chamber. As a result, the striker will be driven in a reciprocal motion within the interior chamber of the housing when the pressurized primary fluid is supplied.
The control sleeve has a front end, a rear end and an interior sleeve chamber defining a passage from the front end to the rear end. The front end of the control sleeve is slidably and sealingly receivable within the interior striker chamber. Whereas, the rear end of the control sleeve is slidably and sealingly receivable within a valve fluid chamber at the rear end of the tool housing. The valve fluid chamber has a first end and a second end. The rear end of the control sleeve is adapted to move toward the first end of the valve fluid chamber during tool advancement. Whereas, the rear end of the control sleeve is adapted to move toward the second end of the valve fluid chamber during tool withdrawal. Additionally, the striker will impact the forward striker surface when the control sleeve is at the first end of the valve fluid chamber and the rearward striker surface when the control sleeve is at the second end of the valve fluid chamber.
The secondary fluid supply assembly is operably connectable to the valve fluid chamber. The valve fluid chamber is pressurized by the secondary fluid supply assembly. The valve fluid chamber must be pressurized to move and hold the sleeve at the first end during tool advancement and the valve fluid chamber must be depressurized to permit the control sleeve to move toward and remain at the second end during tool withdrawal.